Innate immunity to pathogens

P2X7R: a potential key regulator of acute gouty arthritis

OBJECTIVES

Acute gouty arthritis is an inflammatory disease resulting from the precipitation of long-term hyperuricemia-induced monosodium urate (MSU) crystals in joints, which stimulates the production of interleukin-1beta (IL-1β) and initiates an inflammatory reaction. However, some patients having MSU crystals in the joints never develop acute gouty arthritis, indicating that other predisposing factors are required for the disease onset. This review described the mechanism of production of IL-1β by MSU crystals and other possible factors during a gout attack.

METHODS

The relevant English literature on IL-1β secretion stimulated by MSU crystals and other possible factors during acute gouty arthritis flares was searched and carefully reviewed.

RESULTS

MSU crystals lead to the onset of acute gouty arthritis mainly through the activation of Toll-like receptors (TLRs) and NACHT-LRR-PYD-containing protein 3 (NALP3) inflammasome signaling and downstream IL-1β production. The predisposing factors of acute gouty arthritis, such as strenuous exercise, cold, alcolholism, and overeating have a common characteristic inducing dramatic changes of adenosine triphosphate (ATP) in the body. The ATP changes can activate the purinergic receptor P2X ligand-gated ion channel 7 (P2X7R) signaling system to regulate IL-1β secretion.

CONCLUSIONS

We hypothesize that acute gouty arthritis is induced by two synergistic effects; one is the stimulation of MSU crystals and the other is the activation of P2X7R signaling pathways by extracellular ATP changes, which together lead to the production of IL-1β and the initiation of acute gouty arthritis. This hypothesis will provide a new avenue for the prevention and treatment of acute gouty arthritis.

Chitin microparticles for the control of intestinal inflammation

BACKGROUND

Chitin is a polymer of N-acetylglucosamine with the ability to regulate innate and adaptive immune responses. However, the detailed mechanisms of chitin-mediated regulation of intestinal inflammation are only partially known.

METHODS

In this study chitin microparticles (CMPs) or phosphate-buffered saline (PBS) were orally administered to acute and chronic colitis models every 3 days for 6 consecutive weeks beginning at weaning age. The effects of this treatment were evaluated by histology, cytokine production, coculture study, and enteric bacterial analysis in dextran sodium sulfate (DSS)-induced colitis or T-cell receptor alpha (TCRα) knockout chronic colitis models.

RESULTS

Histologically, chitin-treated mice showed significantly suppressed colitis as compared with PBS-treated mice in both animal models. The production of interferon-gamma (IFN-γ) was upregulated in the mucosa of chitin-treated mice compared with control mice. The major source of IFN-γ-producing cells was CD4+ T cells. In mouse dendritic cells (DCs) we found that CMPs were efficiently internalized and processed within 48 hours. Mesenteric lymph nodes (MLNs) CD4+ T cells isolated from chitin-treated mice produced a 7-fold higher amount of IFN-γ in the culture supernatant after being cocultured with DCs and chitin as compared with the control. Proliferation of carboxyfluorescein succinimidyl ester (CFSE)(low) CD4+ T cells in MLNs and enteric bacterial translocation rates were significantly reduced in chitin-treated mice when compared with the control. In addition, CMPs improved the imbalance of enteric bacterial compositions and significantly increased interleukin (IL)-10-producing cells in noninflamed colon, indicating the immunoregulatory effects of CMPs in intestinal mucosa.

CONCLUSIONS

CMPs significantly suppress the development of inflammation by modulating cytokine balance and microbial environment in colon.

[Regulatory B cell and autoimmune disease]

Regulatory B cells that produce IL-10 are now recognized as an important component of the immune system. Hallmark papers from a number of distinguished laboratories have identified phenotypically diverse B cell subsets with regulatory functions during distinct autoimmune diseases, including IL-10-producing B cells, CD5(+) B-1a cells, CD1d(+) marginal zone B cells, and transitional 2-marginal zone precursor B cells. Most recently, a numerically rare and phenotypically unique CD1d(hi)CD5(+)CD19(hi) subset of regulatory B cells has been identified in the spleens of both normal and autoimmune mice. Remarkably, regulatory B cells are potent negative regulators of inflammation and autoimmunity in mouse models of disease in vivo. Herein, our current understanding of regulatory B cell function is reviewed in the context of previous studies that have identified and characterized regulatory B cells.

The development and function of regulatory B cells expressing IL-10 (B10 cells) requires antigen receptor diversity and TLR signals

Autoimmunity and inflammation are controlled in part by regulatory B cells, including a recently identified IL-10-competent CD1d(high)CD5(+) B cell subset termed B10 cells that represents 1-3% of adult mouse spleen B cells. In this study, pathways that influence B10 cell generation and IL-10 production were identified and compared with previously described regulatory B cells. IL-10-competent B cells were predominantly CD1d(high)CD5(+) in adult spleen and were the prevalent source of IL-10, but not other cytokines. B10 cell development and/or maturation in vivo required Ag receptor diversity and intact signaling pathways, but not T cells, gut-associated flora, or environmental pathogens. Spleen B10 cell frequencies were significantly expanded in aged mice and mice predisposed to autoimmunity, but were significantly decreased in mouse strains that are susceptible to exogenous autoantigen-induced autoimmunity. LPS, PMA, plus ionomycin stimulation in vitro for 5 h induced B10 cells to express cytoplasmic IL-10. However, prolonged LPS or CD40 stimulation (48 h) induced additional adult spleen CD1d(high)CD5(+) B cells to express IL-10 following PMA plus ionomycin stimulation. Prolonged LPS or CD40 stimulation of newborn spleen and adult blood or lymph node CD1d(low) and/or CD5(-) B cells also induced cytoplasmic IL-10 competence in rare B cells, with CD40 ligation uniformly inducing CD5 expression. IL-10 secretion was induced by LPS signaling through MyD88-dependent pathways, but not following CD40 ligation. LPS stimulation also induced rapid B10 cell clonal expansion when compared with other spleen B cells. Thereby, both adaptive and innate signals regulate B10 cell development, maturation, CD5 expression, and competence for IL-10 production.